The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Exploring, drilling, completing, and operating hydrocarbon and other wells are generally complicated, time consuming, and ultimately very expensive endeavors. Thus, in order to maximize hydrocarbon recovery from underground reservoirs, hydrocarbon wells are becoming of increasingly greater depths and more sophisticated. For example, wells exceeding 25,000 feet in depth which are highly deviated are becoming increasingly common.
Furthermore, in recognition of the expenses involved in completing and operating such hydrocarbon wells, added emphasis has been placed on well access, monitoring and management throughout its productive life. Ready access to well information and intervention may play critical roles in maximizing the life of the well and total hydrocarbon recovery. As a result, downhole tools are frequently deployed within a given hydrocarbon well throughout its life. These tools may include logging tools to acquire data relative to well conditions, intervention tools to address downhole conditions, and even downhole conveyance mechanisms such as downhole tractors to aid in achieving access to downhole portions of the well which may otherwise be potentially inaccessible.
The above noted downhole tools may be delivered to a downhole location in the well by way of a cable run from the surface of the oilfield. Thus, in order to provide the tools with power and telemetry capabilities, the cable may be configured with conductors and appropriate telemetric features. For example, circumferential forward and return paths of copper may be employed throughout the length of the cable to provide powering and communicative capacity to the downhole tool.
Sizing for the above noted conductors and telemetric features generally increases as the well depth or degree of deviation increases. For example, where the well is of significant deviation, a tractor requiring a significant amount of power may be employed to provide adequate downhole well access. As such, conductor sizing may be increased to help ensure delivery of sufficient power for the tractor. Similarly, in the case of extended reach wells, larger conductors may be employed which offer lower resistance for effective power transmission over greater distances. Furthermore, increases in size for the sake of improved telemetry may also be employed.
Unfortunately, increasing the size of conductors or telemetric features may pose significant drawbacks. For example, as a practical matter, an increase in sizing of cable features also increases the overall weight and profile of the cable. In terms of the increased weight, added load may be imparted on the cable, particularly nearer the oilfield surface. As such, the cable may be susceptible to damage under the stress of its own weight. In terms of an increase in cable profile, adequate sealing for cable deployment in high pressure wells may be compromised. That is, during the manufacturing process sealing sufficient for exposure of the cable to wells exceeding about 5,000 psi may be more of a challenge to attain as the cable profile increases.
In order to overcome the physical challenges posed by larger cables, attempts have been made to deliver such cables via drill pipe. That is, these fatter, heavier cables may be secured to and supported by a drill pipe for deployment into wells of extended depths and/or challenging access. Unfortunately, however, this manner of delivery presents its own set of drawbacks. For example, drill pipe delivery is a very inefficient mode of deployment. It may take about 3 to 4 days to deliver a cable in this manner to the depths of a well exceeding about 30,000 feet. Furthermore, the risk of damage to the cable due to its increased load is replaced with a risk of damage posed by the drill pipe itself. Additionally, delivery via a drill pipe fails to address sealing concerns with the larger profile cable.
For a variety of reasons as noted above, the use of downhole cables exceeding 30,000 feet is generally considered impractical for hydrocarbon well applications, particularly where the wells are of a deviated nature. Whether a matter of load, telemetry, or power limitations, cables substantially exceeding 30,000 feet or so generally remain unavailable and impractical, thereby limiting the effective monitoring and operating of wells exceeding such depths.